Eunyoung Ahn

Epitaxial growth and metallicity of rutile MoO2 thin film

Molybdenum oxides have various crystal structures and physical properties due to the multiple valence states of the 4d molybdenum. Among them, MoO2 has a distorted rutile structure with chemical stability and metallic behavior. In this study we grew epitaxial (100) MoO2 thin films on (0001) Al2O3 substrates. Through careful control of the Ar-partial pressure and growth temperature, we determined the optimal growth condition. From our structural assessments, MoO2 epitaxial thin films with high crystallinity can only be achieved in very narrow growth conditions such as 500 °C and 7 mTorr. The thin film prepared under optimal condition showed good metallic behavior, which was confirmed by electronic transport and optical reflectance measurements. A detailed electronic structure was also investigated by spectroscopic ellipsometry.

Spontaneous Splenic Rupture as a Paradoxical Reaction during Treatment for Splenic Tuberculosis

This report describes a rare case of a patient with splenic tuberculosis (TB) who developed spontaneous splenic rupture after 10 weeks of antituberculous chemotherapy. The patient responded well to the antituberculous regimen prior to the spontaneous splenic rupture. We considered a paradoxical reaction as a cause of the splenic rupture. The patient underwent splenectomy and continuously received initial antituberculous drugs without change. To the best of our knowledge, this is the first report of spontaneous splenic rupture as a paradoxical reaction to antituberculous chemotherapy in an immunocompetent host with splenic TB.

Long-term adherence and persistence with febuxostat among male patients with gout in a routine clinical setting

Abstract Objectives: To assess long-term adherence and persistence to febuxostat (FBX) and factors that might contribute to non-adherence and non-persistence to FBX in male patients with gout during a 3-year period. Methods: Adherence to FBX was assessed by the clinic nurses through pill counts at the scheduled visits and non-adherence was defined as less than 80% of the prescribed dose taken. Non-persistence was defined as discontinuation of FBX longer than 60 days. Results: A total of 220 patients were recruited. The percentage of adherence and persistence was 71.8% and 80.9% at 1 year, 65.5% and 68.2% at 2 years and 58.2% and 56.4% at 3 years, respectively. The logistic regression analysis identified high income status, current smoking, absence of hypertension and previous history of non-persistence with urate-lowering therapy (ULT) as the independent factors associated with non-adherence, and the unmarried, absence of hypertension and previous history of non-persistence with ULT as the independent factors associated with non-persistence. Conclusion: Variable risk factors that are correlated with poor adherence or persistence and easily assessed can be used to identify patients at a particular risk of poor adherence or persistence.

Growth of electronically distinct manganite thin films by modulating cation stoichiometry

Nd1-xSrxMnO3 is a well-known manganite due to close connection among structure, transport, magnetism, and chemistry. Thus, it would be an ideal system to study the modification of physical properties by external stimuli including control of stoichiometry in growth. In this work, we show that an abrupt change of electronic and magnetic properties can be achieved by a subtle change of oxygen partial pressure in pulsed laser deposition. Interestingly, the pressure indeed modulates cation stoichiometry. We clearly observed that the films grown at 140 mTorr and higher showed clear insulator to metal transition and stronger magnetism, commonly found in less hole doping, while the films grown at 130 mTorr and lower showed insulating behavior and weak magnetism. From soft x-ray spectroscopic methods, we clearly observed the compositional difference in those thin films. This result is further supported by scattering of lighter elements in high oxygen partial pressure but not by anion deficiency in growth.Nd1-xSrxMnO3 is a well-known manganite due to close connection among structure, transport, magnetism, and chemistry. Thus, it would be an ideal system to study the modification of physical properties by external stimuli including control of stoichiometry in growth. In this work, we show that an abrupt change of electronic and magnetic properties can be achieved by a subtle change of oxygen partial pressure in pulsed laser deposition. Interestingly, the pressure indeed modulates cation stoichiometry. We clearly observed that the films grown at 140 mTorr and higher showed clear insulator to metal transition and stronger magnetism, commonly found in less hole doping, while the films grown at 130 mTorr and lower showed insulating behavior and weak magnetism. From soft x-ray spectroscopic methods, we clearly observed the compositional difference in those thin films. This result is further supported by scattering of lighter elements in high oxygen partial pressure but not by anion deficiency in growth.